In-situ/self-propelled polishing pad conditioner and cleaner

Abrading – Abrading process – With tool treating or forming

Reexamination Certificate

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Details

C451S443000

Reexamination Certificate

active

06179693

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to polishing apparatus, in particular to a conditioning and cleaning apparatus for use during chemical mechanical polishing of a semiconductor wafer.
2. Description of Related Art
Fabrication of semiconductor integrated circuits (IC) is a complicated multi-step process for creating microscopic structures with various electrical properties to form a connected set of devices. As the level of integration of IC's increases, the devices become smaller and more densely packed, requiring more levels of photolithography and more processing steps. As more layers are built up on the silicon wafer, problems caused by surface non-planarity become increasingly severe and can impact yield and chip performance. During the fabrication process, it may become necessary to remove excess material in a process referred to as planarization.
A common technique used to planarize the surface of a silicon wafer is chemical mechanical polishing (CMP). CMP involves the use of a polishing pad affixed to a circular polishing table and a holder to hold the wafer face down against the rotating pad. A slurry containing abrasive and chemical additives are dispensed onto the polishing pad. The pad itself is typically chosen for its ability to act as a carrier of the slurry and to wipe away the grit and debris resulting from the polishing action.
The wafer and polishing pad rotate relative to each other. The rotating action along with the abrasive and chemical additives of the slurry results in a polishing action that removes material from the surface of the wafer. Protrusions on the surface erode more efficiently than recessed areas leading to a flattening or planarization of the wafer surface.
A key factor in maintaining the performance and longevity of the CMP apparatus is conditioning the polishing pad. Typically, the polishing pad is comprised of blown polyurethane with a felt surface layer containing many small pores to facilitate the flow of slurry to beneath the wafer being polished. There are tiny fingers of polyurethane which are substantially perpendicular to the surface of the polishing pad. An example of such a polishing pad is the model IC-1000 manufactured by the Rodel Corporation, 945 East San Salvador Drive, Scottsdale, Ariz. 85258.
As the number of wafers polished increases, the polishing pad becomes filled with debris formed by the accumulation of chemical reaction products and abrasives from the slurry. This causes the polishing pad to become matted down or to wear unevenly, also known as the “glazing effect”. Thus, it becomes necessary to restore the polishing pad to a state suitable for continued wafer polishing.
The prior art is replete with methods and apparatus used to condition polishing pads. However, almost all the techniques suffer from being cumbersome or complex. The complicated nature of IC manufacturing requires specialized, high cost equipment in terms of price and subsequent operation and maintenance. Therefore, it is a great advantage to having a simple, low cost, low maintenance polishing pad conditioning technique.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a simple, low cost, low maintenance polishing pad conditioner.
It is another object of the present invention to provide an apparatus for in-situ conditioning and cleaning of a polishing pad.
A further object of the invention is to provide a non-motorized, self-propelling polishing pad conditioner and cleaner.
It is yet another object of the present invention to provide a method of conditioning and cleaning a polishing pad while simultaneously polishing a silicon wafer.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
SUMMARY OF THE INVENTION
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, an apparatus for in-situ conditioning and cleaning polishing pads comprising a free-wheeling conditioner head having a top portion and a bottom portion, the bottom portion having a plurality of channels; and a hollow shaft extending from the top portion of the conditioner head connected to a fluid source, wherein fluid is adapted to be delivered into the conditioner head through the hollow shaft to flow along the channels of the conditioner head. The plurality of channels are open to the bottom portion of said conditioner head and radially extend from the center of the conditioner head towards the edge of the conditioner head.
The apparatus for in-situ conditioning and cleaning polishing pads further includes a conditioning pad attachable to the bottom portion of the conditioner head having a plurality of apertures corresponding to the channels of the conditioner head wherein the conditioner head is adapted to deliver fluid from the hollow shaft into the conditioner head along the channels, and out through the apertures of the conditioning pad.
Preferably, the conditioner head has a top portion with means for adjusting the contact force of the conditioner head onto a polishing pad.
Preferably, the conditioner head is circular having a diameter from about the diameter of a wafer holder to about the radius of a polishing pad.
The conditioner head in the first aspect of the present invention is free-wheeling such that contact with a rotating polishing pad causes free rotation of the conditioner head at about the same speed as the rotating polishing pad wherein conditioning and cleaning of the polishing pad occurs during rotation of the polishing pad.
The apparatus for in-situ conditioning and cleaning polishing pads may further include a cantilever attached to the conditioner head. In addition, the apparatus for in-situ conditioning and cleaning may further include an extension and retraction means attached to one end of the cantilever for extending and retracting the conditioner head such that the conditioner head moves radially on a polishing pad allowing conditioning and cleaning of the entire polishing pad.
In another aspect, the present invention relates to a free-wheeling conditioning and cleaning head comprising a freely rotating conditioner head having a bottom portion and a top portion, the bottom portion having a plurality of channels; a roughened disc attachable to the bottom surface of the conditioner head having a plurality of apertures corresponding to the channels of the conditioner head; and a hollow shaft extending into the conditioner head for delivery of a cleansing fluid along the channels of the conditioner head. The free-wheeling rotating conditioner head may further include a means for attaching weights to the conditioning head to adjust the contact force of the conditioning head on a polishing pad.
In a further aspect, the present invention relates to a self-conditioning and self-cleaning polishing apparatus comprising a rotating polishing pad having a surface; a holder for holding an object to be polished against the polishing pad; a free-wheeling conditioner head having a plurality of trenches disposed on the surface of the polishing pad; and a hollow shaft connected to a cleansing fluid source, the hollow shaft extending into the conditioner head to deliver the cleansing fluid into the conditioner head such that fluid flow is directed by the trenches, wherein the rotational energy of the rotating polishing pad propels the conditioner head to freely rotate when contacted with the rotating polishing pad allowing the conditioner head to loosen any debris on the polishing pad and the injection of the cleansing fluid flushes away the loosened debris on the polishing pad.
The self-conditioning and self-cleaning polishing apparatus may further include an agitator secured to a bottom portion of the conditioner head. The agitator comprises a roughened surface having a shape conforming to the shape of the conditioner head, and a plurality of apertures corresp

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